McDonalds used to sell Chicken McNuggets in boxes of six, nine and 20, and then added a box of four McNuggets in a Happy Meal.
Your challenge is to work out the largest number of Chicken McNuggets that it is not possible to buy. That is, by purchasing any number of each of the four box sizes, in any combination, what is the largest number that you cannot buy.
Now that isn't too hard, so once you have solved that, what was the largest number of Chicken McNuggets that you could not buy before the box of four in the Happy Meal was introduced.
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Answer at 9.00 on Monday